I need help with this word problem

Question

 The part time tuition rates per credit hour at a community college were $92 for in-state residents and $255 for out-of-state residents, to take 9 credit hours how much more than an in-state resident does an out-of-state resident pay? 

Answer 1

for each credit hour, the excess charge due to out-of-stateness is $163.

Just multiply this 'differential' by 9 this case.